Resistance mechanism, genetic isolation

In this chapter, the molecular-biological mode of action of macrolide antibiotics and the biochemical and genetic mechanisms of resistance to MLS antibiotics are reviewed. Based on a recent X-ray crystallographic study on a 50S ribosomal subunit from Haloarcula marismortui and the finding of intracellular macrolide accumulation, the mode of action from the viewpoint of a new hypothetical concept, deposition binding, and mechanisms of drug resistance in clinically isolated bacteria are discussed. In addition, recent major developments in macrolide antibiotics are briefly described. 

Enzymatic detoxification was determined to be the major resistance mechanism in all species of mercury-resistant bacteria. For example, mercuric reductase was essential for volatilization of Hg from Hg + and various organomercurial hydrolases were responsible for volatilization of methane (CH4) from methylmercury, for ethane (C2H4) from ethylmercury, and for benzene from phenylmercury. Minamata Bay bacterial isolates can also volatilize Hg from added inorganic and organic mercurials. Genes which govern the chemistry of mercury detoxification were abundant in bacteria found in Minamata Bay and other mercury-polluted sites these genetic strains of mercury-resistant bacteria show promise for bioremediation of mercury pollution. 

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